-- Authorities found similarities in the explosive devices recovered in New York and New Jersey, connecting some of the dots between the multiple incidents over the weekend.
The bombs in New York and Seaside Park, New Jersey, utilized flip phones, although there were differences in design between the devices. The devices in New Jersey were made with pipe bombs; the New York City devices involved pressure cooker bombs.
“You don’t have to be sophisticated. Building a pipe bomb is very easy. A pressure cooker is not that difficult," said May.
However, more sophisticated skills are needed to build the firing switch to set off the bombs, according to May.
The first explosion occurred in Seaside Park on Saturday morning ahead of a military charity run. Nearly 12 hours later, a bomb went off in the Chelsea neighborhood of New York City, injuring 29 people. Police later discovered a second device four blocks away from the explosion. And on Sunday, authorities were alerted to a backpack filled with explosives near a train station in Elizabeth, New Jersey. Law enforcement detonated one of the devices and removed the others without injury.
On Monday, suspect Ahmad Khan Rahami, a naturalized U.S. citizen from Afghanistan, was taken into custody after a shootout with police in Linden, New Jersey.
State, local and federal authorities are still conducting investigations into the explosions.
Both Chelsea bombs were made with pressure cookers. The one that was found intact had a label on it for the chemical Tannerite.
That pressure cooker bomb was described as being extremely heavy and containing shrapnel to maximize injuries, according to a source familiar with the investigation into the device.
Tannerite, an explosive often used for target practice, can be purchased in many sporting goods stores or online. There are no regulations on the purchase of this product.
The color of the Chelsea explosion seen in video is indicative of homemade explosive mixtures, possibly Tannerite, said May.
"If you mass enough of this material, you could do a lot of damage," he said.
Seaside Park explosion
The explosive device that detonated in the NJ shore town involved three pipe bombs tied together and was timed to detonate when the race began, according to a source familiar with the investigation.
One of the pipe bombs exploded, but the race had been postponed and no one was injured.
The different bomb materials may indicate that the suspect may not be a bomb-maker, said May, a certified international post blast investigator.
Authorities recovered five devices in a backpack, one of which exploded during an attempt by a robot to disarm it. This was the third incident over the weekend involving an IED in the New York City area.
Two men had found a suspicious backpack in a garbage can, Elizabeth Mayor Chris Bollwage said in a press conference. The men, who said they believed it may have contained valuables, notified police when they saw wires and a pipe inside the bag. Police immediately brought in the bomb squad.
ABC News' Aaron Katersky and Josh Margolin contributed to this story.