Police in Prince George County (Maryland) tweeted this picture of weapons allegedly seized from the home of Neil Edwin Prescott, who is suspected of plotting a mass killing like the Colorado movie theatre massacre last Friday. (Handout)

Exactly one week after a gunman opened fire in a Colorado movie theatre, killing 12 people and wounding more than 50 others, police in Maryland say they may have foiled a similar plot.

Cops arrested Neil Edwin Prescott, who allegedly told his employer he was "a joker" who would "blow everybody up" and that he would like to see the supervisor's brain splattered on the sidewalk, ABC News reports.

The joker comment seemed to reference James Holmes, the suspect in last Friday's Colorado shooting, who dyed his hair red and told police he was The Joker from the Batman movies.

ABC News cites law enforcement sources who claim Prescott had a cache of weapons at his home in Crofton, including semi-automatic rifles, shotguns, handguns and thousands of rounds of ammunition.

Prescott was facing termination from his job at Pitney Bowes, and made the threats in two phone calls to his supervisor, Prince George County Police Chief Mark Magaw said in a press conference.

Maj. Henry Stawinski, of the force's Bureau of Forensic Science and Intelligence, said when police arrived at Prescott's house on Thursday, he was wearing a T-shirt that read "Guns don't kill people, I do."