PHILADELPHIA (WPVI) --Although Omar Mateen was once on a terrorist watch list, that didn't stop him from purchasing two weapons, a day apart from each other at a licensed gun dealer the week before the mass shooting.
Now as Orlando mourns, there are cries for answers about how he slipped through the cracks.
"It is almost impossible to stop all of these attacks," Senator Tom Carper of Delaware said Monday.
Carper, the ranking member on the Senate Homeland Security Committee, speculated about why no alerts were raised when suspected terrorist Mateen purchased two high powered guns.
"The idea of somehow allowing people on our terrorism watch list to buy weapons, my dad would have said that's crazy," Carper said.
Mateen worked as a security officer at G4S Solutions, one of the world's largest private security companies, based in Florida.
"He may have used his licensure, his registration with the state screening agency, to be able to buy a weapon," Carper said.
In Philadelphia, Mayor Jim Kenney criticized what he says are lax laws across Pennsylvania and across the nation.
"The only purpose for an assault weapon is to kill people, which we have seen, it is very effective in doing that," Kenney said.
Kenney was part of City Council when they tried to tighten gun permitting laws in Philadelphia, but the city's law was superseded by the state and never enforced.
"I don't know how we keep people safe," Kenney said.
In Pennsylvania, the State Police say most gun licensees are approved in a matter of minutes.
"If your record is completely clean, no issues with a protection from abuse or domestic violence, yes, you could be in and out of a store in a few minutes," Corporal James J. McFadden said.
And Mateen's license likely would have been approved here, too. He was removed from the FBI watch list in 2014.
"I think a person who has been tangentially connected to terrorism should not be able to purchase an assault weapon," Kenney said.
"Whether we think that we can pass legislation that denies someone on a watch list the ability to buy at least assault weapons that is a shot we should take," Carper said.
The Senate had considered a ban on buying weapons by suspected terrorists back in December, but that bill did not have enough support to pass.
Carper says the FBI has the capability to track the gun purchases of people on the watch list, and he says, that is exactly what needs to be done.