Senator Bill Nelson of Florida reiterated to reporters in front of Orlando’s Pulse nightclub Sunday night that the shooter responsible for the deadliest mass murder in American history at that club Sunday morning was a “lone wolf,” and he could not confirm “with certainty” that Islamic jihadist ideology led the shooter to perform his crime.

“It’s hard to be 100 percent when you are dealing with a lone wolf,” Senator Nelson told reporters before being approached by Tom Trento of the United West, who asked the Senator plainly whether “the ideology of Islamic jihad” drove Omar Saddiqui Mateen to attack the club during LGBT pride month.

“I cannot tell you with certainty that it is, but it has all the appearances because of the connection with someone who had been to Syria,” Sen. Nelson told Trento. “At the same time for him to have planned it… [on] such a vulnerable target of a lot of people, 300 people in a closed environment… that is a recipe for someone that wants to do harm,” he added. “Unfortunately, there are a lot of grieving people here.”

Sen. Nelson also refuted the concept of the “known wolf,” described by Trento as the belief that “no one is independent of some network – a mosque or others.” Some attackers, he argued, are “dark and there’s no connection.”

Pressed on whether internet ties to a terrorist network would negate the idea of a “lone wolf” shooter, Sen. Nelson responded that, if the shooter in this case had internet ties to a terrorist cell, “we ought to be able to pick up some of that.” “We’ve got a great intelligence apparatus… if he would have been communicating with something, we would have picked that up.”

Omar Saddiqui Mateen, a U.S. citizen of Afghan descent, opened fire in the densely packed Pulse LGBT nightclub in Orlando, Florida early Sunday morning, killing 50 and injuring over 50 others. He is known to have attended services at the Islamic Center Fort Pierce for over 13 years and had been investigated for potential terrorist ties by the FBI in 2014.

Sen. Nelson had confirmed to CBS News this morning that intelligence sources working with the FBI had evidence that Mateen had a “connection” to the Islamic State terrorist organization, though he did not specify the nature of that connection.

The shooting is the deadliest in the history of the United States.

Watch the interview with Sen. Nelson below: