A pair of explosions less than two hours apart sparked a massive police investigation in and around the Sherwood Park community centre on Tuesday evening, RCMP say.

The first explosion happened at about 6:30 p.m. in the Strathcona County Community Centre's parkade. Soon after police arrived at the scene they found an injured suspect inside a vehicle.

The 21-year-old man was taken to hospital, where he later died.

A second explosion in the parkade happened at about 8:15 p.m. while the emergency response team and the explosive disposal unit (EDU) were investigating at the scene. No one was injured.

At a news conference Wednesday afternoon, RCMP said they are not looking for any other suspects and the public is in no danger.

"We don't yet have a motive for this incident," Supt. Dave Kalist told reporters.

Police said the "cause and origin" of the two explosions is still under investigation.

"The EDU team will remain on scene and the area secured until they are able to determine the cause of the explosion and ensure there are no other potential threats," police said in a news release.

Kalist said the RCMP Major Crimes Unit is leading the investigation.

'The speculation is not helping'

Police remained on scene overnight Tuesday after a fire broke out inside the Strathcona County Community Centre in Sherwood Park. (CBC)

Emergency crews and tactical units swarmed the building Tuesday after witnesses reported hearing an explosion inside the parkade. A nearby home for seniors was evacuated and road blocks were erected in the area.

Strathcona County Mayor Rod Frank reassured the public it was no further danger.

"It's an unusual situation for our community and we all know what modern times are like but the main point right now is that this is under control, and the speculation is not helping," he said Wednesday.

Frank said the Community Centre and County Hall buildings will remain closed to provide the RCMP "with the room they need for their investigation."

Throughout the night, heavily armed officers could be seen moving in and out of the community centre complex, which houses the county's council chambers as well as the library, meeting rooms and outdoor plazas.

On Wednesday, all entrances to the building remained blocked off by police. St. Theresa school and Salisbury Composite High School also remained closed for the day.

This is the scene at the corner of Festival way and Sherwood drive. Traffic heading south across from the mall still be rerouted. Heavy RCMP police presence at all entrances to the community centre. <a href="https://twitter.com/hashtag/ShPk?src=hash&ref_src=twsrc%5Etfw">#ShPk</a> <a href="https://t.co/srONauoNk1">pic.twitter.com/srONauoNk1</a> —@MinDhariwal

An RCMP officer on the scene told CBC News there are no active evacuations in place. The officer said police are focused on keeping people away from the parkade underneath the library.

Jim, who asked that his last name not be used, was on the main floor of the library when the building began to shake.

There was rattling coming from the parking garage below.

"I hunt and I've been around firearms my whole life, and I'm aware of what loud bangs and booms are," he said. "This was a violent explosion. It shook the building. The boom lasted seconds.

"The concrete under our feet shook. Our chairs shook."

Chelsea Thoen describes the 'huge bang' she heard from Strathcona County Community Centre on Tuesday night. 0:31

As the fire alarms began wailing, Jim, his partner and their group went outside to the parking lot, where emergency vehicles had begun to arrive.

Jim wanted to retrieve his vehicle from the parkade. He walked down the entrance ramp and through the overhead door, which was jammed wide open.

"As we walked around the corner, the lights were still on down there but there was a hue in the air," he said. "I'm not sure what it was. It didn't smell like smoke and it left sort of an acidic taste in my mouth.

"My eyes burned. My throat burned."

While police have not confirmed that any kind of blast occurred inside the building, Jim said he has no doubt there was an explosion.

"It was a large explosion," he said. "Nothing small about it."