Police are searching for two individuals seen leaping from one of Pittsburgh’s tallest buildings.

The jumpers were recorded on CCTV entering 1 PPG Place around 4:45 AM on Apr. 9, before heading to the top of the building and parachuting off.

The jumpers are speculated to be participating in BASE jumping, an extreme sport where participants leap from tall fixtures or buildings to parachute down from them. BASE is an acronym meaning buildings, antennas, spans (bridges), and Earth (cliffs/mountains), which states the terrain the jumpers aim to parachute from.

Jumping from 1 PPG Place was not sanctioned, and police are attempting to charge the two jumpers with trespassing.

There are sanctioned BASE jumping events, an example of which is Bridge Day in Fayetteville, West Virginia, where thousands of people BASE jump from the New River Gorge bridge into the valley below.

This is not the only example of people BASE jumping from Pittsburgh landmarks. On May 18, 1986, two BASE jumpers lept from the US Steel Tower right before the beginning of the Pittsburgh Marathon. Following their landing, the jumpers escaped in one of their friend’s vans and evaded police capture.

The man videoing the event for the jumpers, however, was arrested and charged with trespassing.

BASE jumping is illegal in most cities, as well as in all National Parks, with the reasoning being the sport is “reckless and dangerous.”

Police in Zone 2 are actively pursuing this case, and are looking for leads.