Ironman athlete Brian Kozera -- who was also a police officer and cancer survivor -- has tragically died at 44 years old ... after he was involved in a terrifying bicycle crash while he was training for an upcoming competition.
Kozera -- a 16-year veteran of the Norristown Police Dept. -- passed away after he struck a car on Saturday while he was biking in Caernarvon Township, PA.
According to a crash report, obtained by TMZ Sports, at around 9:48 AM ... Brian ran a stop sign and hit the passenger side of a pickup.
Kozera, according to the docs, was thrown from his bike and ended up being caught in the car's rear wheel. Cops say he was transported to a nearby hospital, but died from the injuries he suffered in the accident.
Kozera had been training for the Ironman World Championships in Hawaii in October 2022 ... according to a statement from the Norristown Fraternal Order Of Police Lodge 31.
In 2014, Kozera was diagnosed with a rare cancer called Lymphocyte-depleted Hodgkin’s lymphoma. He later beat it in 2015 -- and said his battle with the disease gave him the push to become an Ironman athlete.
Kozera was slated to compete in three more events leading up to the competition in Hawaii ... before his untimely death, according to his blog.
Brian is survived by his wife and three young daughters.