Philadelphia authorities on Wednesday criticized people for not reporting suspicious behavior by the alleged gunman in Monday’s mass shooting that killed five people and injured two children.

Kimbrady Carriker, 40, is accused of opening fire in a southwest Philadelphia neighborhood using an assault-style rifle. Carriker was arrested shortly after the shooting and charged Wednesday morning with five counts of murder. He also faces charges of attempted murder, reckless endangerment, aggravated assault and carrying a firearm without a valid permit. Carriker is being held without bail.

Officials say the gunman’s targets appear to have been selected at random.

During a news conference Wednesday, Sheriff Rochelle Bilal said there were “disturbing messages” found on a social media page belonging to Carriker. Bilal did not go into detail about the messages. 

“Let us use this opportunity to reexamine social media posts we may see that mention harming someone or suggest extreme activities,” Bilal said. “If you know this person or see a post that raises a red flag, you have to speak up and call the authorities immediately. This is our business, and we can't afford to stay silent.”

Philadelphia Assistant District Attorney Joanne Pescatore said the seven people who lived with Carriker witnessed him “exhibiting abnormal behavior for quite a while,” including wearing a bulletproof vest and having guns inside the house, but they did not alert authorities. One of them described Carriker as “getting more and more agitated” in the days leading up to the shooting.

“I'm not blaming anybody, but if anybody out there has such a situation as this, maybe, maybe just call call somebody,” Pescatore said. “Call anonymously … and maybe he could have gotten help before this became what it did.”

Among the items found during a search of Carriker’s home were live rounds of ammunition that matched what was found at the crime scene a will dated June 23, said Assistant District Attorney Bob Wainwright.

Killed in the shooting were Lashyd Merritt, 22; Dymir Stanton, 29; Ralph Moralis, 59; Daujan Brown, 15; and Joseph Wamah Jr., 31.

At the news conference, Josephine Wamah, Joseph Wamah’s twin sister, said, “I still can’t believe my brother is gone.”

“I just don't understand why this is happening,” she said. “Like, he was a kind soul. He was nice to everyone. He was good to everyone.”

Jasmine Wamah, Joseph and Josephine’s sister, had a message for the shooter: “Why don’t you just kill your [expletive] self? You should’ve shot yourself. I’ve got nothing but anger.”

The news conference was called by District Larry Krasner, but he only spoke briefly about the case himself and instead called on law enforcement officials, medical professionals, faith leaders and others to speak about the shooting, help available to the victims’ families in the aftermath, and gun violence in general. 

Krasner, however, said, “Obviously, this office is 100% committed to the vigorous prosecution of this mass killer, and we will do justice in court with this case.”