Johna Batiste, a Washington State policeman, took to Twitter to seek help in an ongoing investigation into a deadly hit-and-run accident, which supposedly involved a "black vehicle."
The trooper posted a picture of a bicycle wreck and a car part from a vehicle that allegedly killed a cyclist, asking the public for any information on the collision.
The tweet sparked the attention of Redditors; one of them, a former Maryland state inspector going by nickname JeffsNuts, identified the part as a headlamp assembly of a 1986 Chevrolet Silverado truck.
A few days later, Batiste tweeted an update, saying WSP detectives had arrested the suspect, who turned out to be the driver of a 1986 Chevy K-10.
Twitter users gave credit to the one sharp-eyed Redditor that helped the police seek out the culprit.