PHILADELPHIA (Reuters) - The gunman who claimed allegiance to Islamic State after shooting a Philadelphia police officer was described by people who knew him as a devout, quiet Muslim who became more “combative” after trips to Egypt and Saudi Arabia.

Philadelphia Police Department image shows the gunman Edward Archer of Philadelphia this Philadelphia Police Department image released on January 8, 2016. REUTERS/Philadelphia Police Department/Handout

As police charged Edward Archer on Saturday with attempted murder, aggravated assault and assault of a law enforcement officer, investigators continued to examine what prompted the 30-year-old construction worker to open fire on a police car.Two people who knew him described a pious man who began expressing interest in Islam in his teenage years and devoted his life to religion. He participated in a local Muslim football league and worked on construction jobs, they added.They said they did not understand why, at nearly midnight on Thursday, he approached officer Jesse Hartnett, 33, and fired 11 rounds, some at point-blank range, through the car window. Three shots struck the officer in his arm.Archer later confessed to the attack and said he pledged allegiance to Islamic State, police said. FBI Special Agent Eric Ruona said Archer had traveled to Saudi Arabia in 2011 and Egypt in 2012 - a trip that a family friend said changed him.

“He became more drastic. More combative,” said Jannah Abdulsalaam, who asked only to be identified by her Muslim name. “He was kind but I noticed that change.”

The attack comes at a time of heightened anxiety in the United States over the threat posed by Islamic State. A Muslim couple inspired by the militant group killed 14 people on Dec. 2 in San Bernardino, California, just weeks after gunmen linked to the Islamic State group killed 130 people in Paris.ARABIC STUDIESArcher studied Arabic at a local mosque a few years ago, said members of the mosque. Kevin Washington said Archer was “OK” at the language before even signing up for classes. Washington and another acquaintance say Archer used to talk about football.

Video of the attack shows a man in a long robe similar to the traditional dishdasha, or thobe, often worn by Muslim men in parts of the Middle East, as he opened fire on the police car.

Police officers nearby arrested him.

In 2013, Archer was charged with aggravated assault. At the time of the shooting, he was awaiting sentencing on forgery charges in Delaware County, where he lived. He also pleaded guilty in 2014 to assault and carrying an unlicensed gun, Abdulsalaam said Archer called her “Aunty”, or “Sister Jannah,” and used to check on her or occasionally buy her groceries.

She lived about a block away from a two-story row house in a working class West Philadelphia neighborhood where Archer was believed to have stayed at times and where investigators searched for evidence on Friday, not far from the intersection where Hartnett was shot.

She said that while Archer was “exceptionally knowledgeable” about Islam, there may have been an “overload” of information that led him to become radicalized.”There’s so many people who have been swayed to go in that direction. ISIS needs to be destroyed,” Abdulsalaam said, using an acronym for Islamic State militants who have seized parts of Iraq and Syria, declared war on the West and proclaimed a “caliphate” that would rule over all Muslims.Jacob Bender, executive director of the Philadelphia chapter of the Council on American-Islamic Relations, said Archer’s actions did not represent those of Muslims or the Islamic faith.Police have said it is unclear whether he was radicalized or had ties to militant groups.Washington said he was unsure what had led Archer to shoot a policeman.Natalie King, 68, a neighbor and retired public worker said that while Archer was seen going to a mosque each Friday, she did not consider him radicalized. She said she thought his actions might have been the result of a mental illness. Police Commissioner Richard Ross said on Friday there was no sign that he had worked with anyone else.

In an interview with the Philadelphia Inquirer on Friday, Archer’s mother said her son had suffered head injuries from playing football and from a moped accident several years ago.