An explosion last fall in the parkade at the Strathcona County Community Centre was likely triggered by Tannerite hidden in a pickup truck, Strathcona County RCMP said Tuesday.

A second explosion later the same evening was caused by an overheated gas tank in another vehicle in the parkade, police told a news conference.

Traces of nitrate salts and aluminum powder found in debris were sent for testing, police said, but the samples were degraded so the lab could not identify the exact substance used.

"Nitrate salts and aluminum powder can be found in a number of products, including binary explosive, or 'target shot' such as Tannerite," RCMP said in a news release.

The first explosion happened at about 6:30 p.m. on Nov. 6, 2018. When police arrived at the scene, they found an injured 21-year-old man inside a vehicle. Kane Kosolowsky later died of a self-inflicted gunshot wound.

The second explosion in the parkade happened at about 8:15 p.m. while emergency crews were investigating.

Tannerite, which can be purchased in sporting goods stores, is used for target shooting.

"Based on the lab results and further investigation into Kane Kosolowsky's familiarity with the substance and method of ignition, the RCMP believe it is likely Tannerite was the explosive used," the RCMP statement said.

The police behavioural sciences group will review the evidence to try to determine, if possible, what motivated Kosolowsky to set off the explosion and shoot himself, the news release said.

There is no evidence linking the explosion to any terrorist group or threat, police said. The evidence, including video surveillance and background investigation, indicates that Kosolowsky acted alone.

"While there are questions that are unanswered, and the investigation will remain open, this is the final piece of substantive information that we will have to offer the public," said RCMP Supt. Dave Kalist.

"I would personally like to thank the Strathcona County officials and the Kosolowsky family for their continued co-operation."

Criticism has been levelled at the county's response to the incident, particularly in connection with the fact that officials remained mum on the unfolding drama as speculation and panic filled social media channels.

It wasn't until about 1 a.m., more than six hours after the incident began, that Strathcona County issued a statement urging people to avoid the area due to a "police matter."

While the substance used in the explosion is now confirmed, RCMP may never know the motive behind Kosolowsky's actions, Strathcona County Mayor Rod Frank said Tuesday.

"What I do know is this: Strathcona County weathered an intentionally-set explosion in the heart of our community and we were able to come together and respond with great resiliency," Frank said in a statement.

"As we approach the one-year mark of this explosion, it's important to recognize the impact this isolated incident had on some members of our community, especially patrons, tenants and county staff who live or work near the community centre."