Police said a device found inside a bag had wires, an electrical circuit board of some sort, a container of fluid and a metal pipe. It was left in landscaping outside the west end of the Mosteller Garage in the first block of East Chestnut Street, police said.
"Without getting into any specifics ... somebody obviously intended to do harm. It certainly was a dangerous device," said West Chester Police Chief Scott Bohn.
About 6:30 a.m., someone noticed a suspicious person dressed in black who was possibly carrying a bag in an alley near the garage, police said.
Then, about 7:15 a.m., several people in the five-story garage told an attendant about a suspicious person on the west side of the garage, police said. When the attendant investigated, he reportedly noticed a man wearing black pants, a black sweatshirt with a hood over his head and a black hat overtop.
After the attendant saw the man in black leave the area, he noticed a bag with wires outside the garage, prompting him to call police.
While investigating, authorities located two other suspicious packages, both of which were detonated by the Montgomery County Bomb Squad. But these were not explosive devices and do not appear to be connected to the bomb, authorities said.
The suspicious device was rendered safe Monday afternoon, according to John Durante, Montgomery County sheriff and head of the region's bomb squad. Durante said he would not discuss how potentially dangerous the device may have been until it has been analyzed in a laboratory.
The bomb will be sent to the Bureau of Alcohol, Tobacco and Firearms' lab in Ammendale, Md., according to ATF special agent John Hageman.
"This device was put together by someone who has some knowledge of explosives," Hageman said.
At the lab, investigators will compare the evidence to items tied to the so-called Suburban Bomber, who detonated explosives in the Phoenixville area from March 2000 to November 2001. During that span, local and federal authorities encountered roughly 13 bombs, of which six had detonated. All were considered to be the work of the same bomber, who was never caught.
The comparison should not suggest any direct link between Monday's bomb and the Suburban Bomber, Hageman said. The items will be compared due to the nature and close proximity of the crimes, he said.
Also, Hageman said no evidence suggests Monday's incident is connected to two devices found in Montgomery County last month.
"Right now, it would not appear they are related," Hageman said.
FBI and Chester County detectives are also helping with the investigation. Authorities have been reportedly viewing surveillance video from the surrounding area to learn more about who may have left the device.
Roughly a one-block radius around the garage was evacuated for the most part, including the YMCA, which has a daycare.
The incident prompted several road closures, leading to traffic congestion for most of the day. About 5 p.m., most roads were reopened and motorists were allowed to retrieve their vehicles from the garage. A portion of the garage was still considered a crime scene Monday night.
Police were initially looking at an electrical panel on the second floor of the garage, which is supposed to be secure but had been left open. But Monday afternoon, police said there appeared to be no connection between the open panel and the bomb.
Monday's excitement interrupted what would normally be a bustling afternoon downtown. Instead, the streets were eerily empty as handfuls of people watched authorities investigate.
Matthew Hopkins of Haverford said he normally parks his car in the Mosteller Garage, which is across the street from his office. Instead, he had to park at a street meter.
"This is by far the craziest it's ever been in West Chester," Hopkins said as he waited to get back to work. "It's kind of exciting, but scary at the same time."
Authorities were on hand for most of the day. Bomb-sniffing dogs from Tredyffrin, West Caln, and the Chester County Sheriff's Department helped search the garage.
Authorities urge anyone who may come across a suspicious package to report it to police immediately.
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