The perpetrator of this weekend’s mass shooting in an Orlando nightclub may have been inspired by radical jihadist material on the internet, President Obama said in a briefing today. It’s unclear how that material was accessed, but ISIS is known to be active on Twitter, Telegram, and YouTube, among other networks.

In a separate briefing, FBI Director Comey confirmed that conclusion, saying "we are highly confident that this killer was radicalized at least in some part through the internet."

The government’s investigation into the attacker is still ongoing, but the president referred to it as an apparent act of "homegrown terrorism," saying there is no reason so far to believe that the attack was commissioned or planned by ISIS leaders overseas." At this stage, we see no clear evidence that he was directed externally," President Obama told reporters.

Still, the killer clearly saw himself as acting on behalf of ISIS, swearing allegiance to the group in a 911 call before the attack. ISIS leaders have since reciprocated, publicly accepting responsibility for the horrific attack. The exact nature of the attacker's ties to ISIS are still being investigated.

For now, the incident appears to be a lone-wolf attack inspired by radical jihadism, similar to the shooting in San Bernardino last year. Investigators in that case also referred to the attackers’ online activities as a key motivation. In a public press conference after the shooting, FBI director James Comey claimed the couple had been radicalized after "consuming poison on the Internet."

Update 12:33 PM ET: Updated with information from FBI briefing.