PHILADELPHIA (AP) — A tense Philadelphia braced for more demonstrations Wednesday over the police killing of a Black man following two nights of protests that set off clashes with police and break-ins of stores on the other side of the city.

The death of Walter Wallace Jr., who was fatally shot by police Monday after authorities say he ignored orders to drop a knife, came amid already heightened tensions in the battleground state just days before the election. City officials announced Wednesday they would enact a curfew in the city from 9 p.m. until 6 a.m.

About 500 people gathered in a West Philadelphia park Tuesday evening, marching to the nearby police headquarters where officers were stationed with riot shields. Some of the demonstrators threw debris at officers, according to police, and both sides later clashed.

Police said two officers were injured, although authorities did not disclose the extent of their injuries.

Some business owners were cleaning up damage and boarding up windows and doors Wednesday after video showed people streaming into stores and stealing goods on the opposite side of the city from where Wallace was shot. The National Guard is slated to arrive in the next few days to focus on guarding infrastructure, state and city officials said.

The clashes come as Pennsylvania emerges as a key focus of the contentious 2020 election, with President Donald Trump and former Vice President Joe Biden, a native son, locked in a battle for the state’s 20 electoral votes. Both candidates have made frequent campaign stops in the state.

More than 9 million Pennsylvanians have registered to vote, and many in Philadelphia waited in line for hours this week to request a mail-in ballot by Tuesday's deadline, as news of the police shooting spread.

Mayor Jim Kenney, a Democrat, said Tuesday the city had been through “a very difficult time,” but said vandalism was not the answer.

“There were a lot of peaceful protesters out there last night,” Kenney said at a news conference on Wallace’s death. However, he said. violence “is not an acceptable form of First Amendment expression.”

A Kenney spokesperson said Wednesday the city has requested help from the Pennsylvania National Guard to help with “the current situation and election preparation.” Specific details were still being worked out, and none have yet been deployed.

The unrest started Monday evening, shortly after Wallace, 27, was killed, and set off protests elsewhere, including in Washington, D.C., the Brooklyn borough of New York City and Portland, Oregon, where demonstrators held their hands in the shape of a “W" in his honor.

Police said Wallace was wielding a knife and ignored orders to drop the weapon before officers fired shots Monday afternoon. But his family's lawyer said the family had called for an ambulance to get him help with a mental health crisis. His parents said Tuesday that officers knew their son was in a mental health crisis because they had been to the family’s house three times on Monday.

Wallace's wife, Dominique, is pregnant and was scheduled to be induced Wednesday, according to the family’s attorney, Shaka Johnson. Johnson said Wallace had nine children, two of whom briefly spoke at a news conference late Tuesday, along with Wallace’s mother and father.

“When you come to a scene where somebody is in a mental crisis, and the only tool you have to deal with it is a gun ... where are the proper tools for the job?” Johnson said, arguing that Philadelphia police officers are not properly trained to handle mental health crises. Johnson said Wallace’s brother had called 911 to request medical assistance and an ambulance.

Police officials said they could not confirm what information had been given to the responding officers, whether they were told about a possible mental illness or how many calls they had received for help at Wallace’s address Monday. Chief Police Inspector Frank Vanore confirmed that police had received a call before the fatal encounter Monday about a man screaming and saying that he was armed with a knife.

Police Commissioner Danielle Outlaw said the officers involved in the shooting were taken off street duty as they investigate. Outlaw said the officers’ names and other identifying information, including their race, would be withheld until the department could be sure releasing the information would not pose a threat to their safety.

Neither had a Taser or similar device at the time of the shooting, Outlaw said, noting the department had previously asked for funding to equip more officers with those devices.

The two officers each fired at least seven rounds — at least 14 total shots — but Vanore could not say how many times Wallace was struck.

Wallace’s father, Walter Wallace Sr. said Tuesday night that he is haunted by the way his son was “butchered."

“It’s in my mind. I can’t even sleep at night. I can’t even close my eyes,” he said.

In video filmed by a bystander and posted on social media, officers could be seen yelling for Wallace to drop a knife. In the video, Wallace's mother and at least one man followed Wallace, trying to get him to listen to officers, as he briskly walked across the street and between cars.

Wallace advanced toward the officers, who then fired several times, said police spokesperson Officer Tanya Little. Wallace's mother could be seen screaming and throwing something at an officer after her son was shot and fell to the ground.

The video does not make it clear whether he was in fact holding a knife, but witnesses said he was. Police would not confirm any details about the weapon Wallace was alleged to be holding Tuesday, saying it is still part of the open investigation.

Wallace was hit in the shoulder and chest, Little said. One officer drove him to a hospital, where he was pronounced dead a short time later, she said.

Lawyer Robert Trimble represented Wallace in a 2016 robbery case that led him to spend about a year in jail. His sentence, according to court records, included six years of probation and mental health supervision. He had new charge pending at the time of his death.

“I ran into him about a year ago by City Hall. He stopped me on the street and thanked me for helping him,” Trimble said. “I remember him being a decent guy.”

Wallace's death set off demonstrations Monday night, leading to the arrest of more than 90 people. Police said 30 officers were injured Monday, most of them hit with objects like bricks.

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Associated Press writer Maryclaire Dale contributed to this report from Philadelphia.