By Brad Segall

NORRISTOWN, Pa. (CBS) — Law enforcement authorities in Montgomery County have released surveillance video of a man they are calling a “person of interest” in connection with last week’s bomb threat at the courthouse in Norristown.

The video was taken from a 7-Eleven store along Main Street in West Norriton. It shows a man on a pay phone outside the store.

The first call was made just after 8:30 last Thursday morning with an unidentified caller telling Norristown police there were bombs and explosives in the courthouse. A second call just minutes later from a cell went to the county’s emergency operations center. District Attorney Risa Ferman hopes the public can help them identify the man.

“We are following up on a number of specific leads,” Ferman says, “and we anticipate identifying the individual or individuals involved and taking severe action as it relates to their conduct.”

The courthouse was evacuated for about two hours. No explosives were found.

Still image of "person of interest" from surveillance video outside of 7-Eleven along Main Street in West Norriton. (credit: Montgomery County District Attorney's Office)

Still image of “person of interest” from surveillance video outside of 7-Eleven along Main Street in West Norriton. (credit: Montgomery County District Attorney’s Office)

Still image of "person of interest" from surveillance video outside of 7-Eleven along Main Street in West Norriton. (credit: Montgomery County District Attorney's Office)

Still image of “person of interest” from surveillance video outside of 7-Eleven along Main Street in West Norriton. (credit: Montgomery County District Attorney’s Office)