FBI is trying to confirm the suspect's identity through biometrics and DNA

Kevin Rojek, the special agent in charge of the FBI Pittsburgh office, said in a news conference that the agency is working on identifying the gunman through “doing biometric confirmations” because the suspect did not carry identification on him.

“We’re looking at photographs right now, and we’re trying to run his DNA and get biometric confirmation,” he said.

When asked whether authorities knew what kind of gun was used or how many shots were fired, Rojek said authorities did not have that information. Lt. Col. George Bivens of the Pennsylvania State Police followed up by saying that officials had “a good idea of what the weapon was” but that it was still part of the investigation.

Authorities are also investigating how the shooting took place — including reports by eyewitnesses that they saw the gunman climbing up a roof.

A witness told BBC News he saw the suspect on the roof with a rifle and tried to notify police before the incident. CNN cannot independently verify his account.

Bivens said that officials were aware of this testimony and that “law enforcement had responded to a number of reports of suspicious activity.”