Christopher Pekny was working on an explosive for a gender-reveal stunt when it blew up, according to New York State Police.

With the help of the police bomb unit and clandestine lab team, a search turned up 17 firearms -- some loaded-- and thousands of rounds of ammunition, as well as a pipe bomb.

Sayoc earlier this year had pleaded guilty to explosives charges for mailing 16 pipe bombs days before the midterm elections last fall.

Sayoc, 57, shackled at the ankles, briefly sobbed as he entered the plea before a New York federal judge.

An exploded pipe bomb was found in a garbage can in Banff National Park on Tuesday, according to RCMP.

Swift Current RCMP say they found an improvised explosive device while conducting a condition check for a 17-year-old boy who was on probation.

Elizabeth Lecron, 23, told undercover FBI agents that she wanted to carry out an "upscale mass murder" at a Toledo bar.

The Federal Bureau of Investigation said on Twitter it recovered a package on Thursday night that was similar to other recently mailed parcel bombs to prominent Democrats and critics of Trump.

Pipe bomb suspect Cesar Sayoc searched for addresses of his targets online and had photos of many of them on his cellphone, federal prosecutors said in a letter outlining more evidence against him.

American documentary filmmaker Michael Moore has released previously-unseen footage of pipe bomb suspect Cesar Sayoc in attendance at a Trump rally in early 2017.