BOSTON (KDKA/AP) – Massachusetts Gov. Deval Patrick said no unexploded bombs were found at the Boston Marathon. He said the only explosives were the ones that went off Monday.

Three people were killed, including an 8-year-old boy, and more than 150 injured by two explosions just seconds apart near the finish line.

READ MORE: 'I Just Got A High IQ:' Antonio Brown Downplays Mental Health Issues To 'CBS Mornings'

Special Agent in Charge Richard DesLauriers said at a news conference that there are no known additional threats.

Police Commissioner Ed Davis said it is the most complex crime scene in history of the department.

KDKA-TV’s Andy Sheehan had crossed the finish line of the Boston Marathon just minutes before the blasts.

Andy was walking shoulder to shoulder with hundreds of other runners when the first blast shook the street and buildings.

He turned around in time to see a second blast, and smoke coming from the finish line area.

READ MORE: High Winds Fan Flames Of 4-Alarm Fire At Former Butler Co. Business

Authorities are looking for amateur video and photographic evidence that can give clues as to who set off the bombs.

“What occurred in Boston was an act of cowardice,” Suffolk County District Attorney Daniel Conley said.

Vince Chavanon was excited to be running his first Boston Marathon. The 26-year-old was celebrating with friends on Boylston Street near the finish line when they heard a bang and then another.

“Honestly, it was terrifying. We didn’t know what happened. We saw smoke and we saw people running in both directions,” Chavanon said.

Stay With For More Details

MORE NEWS: Kennywood, Sandcastle, Idlewild Looking To Hire More Than 2,000 Workers For Upcoming Season

3 Dead, At Least 130 Injured In 2 Bombings Near Boston Marathon Finish Line
KDKA’s Andy Sheehan With A First Hand Account Of Marathon Bombings
Local Runners Describe Terrifying Moments At Boston Marathon