Billy Chastain, 30, Mark Chastain, 32, Alex Stevens, 29, and Mike Sparks, 32, are pictured in provided images by police. (Credit: Okmulgee Police Department) OKMULGEE, Okla. - Authorities in Oklahoma are searching for a person of interest after the disappearance and gruesome killing of four friends, who were found shot and dismembered in a river.Police in Okmulgee, a city located about 40 miles south of Tulsa, said on Monday that the dismembered remains discovered last week belonged to missing individuals Mark Chastain, 32, Billy Chastain, 30, Mike Sparks, 32, and Alex Stevens, 29.Okmulgee Police Chief Joe Prentice on Monday told reporters that all four men were shot and severely dismembered before being placed in the river."I’ve worked over 80 murders in my career, involving multiple victims, dismemberment, but this case involves the highest number of victims, and it’s a very violent event," Prentice told reporters. "Can’t say I’ve never worked anything like it, but it’s right up there at the top."The four friends left Billy Chastain’s home around 8 p.m.
on Oct. 9, all riding bicycles, Prentice said. Investigators believe the men had planned to "commit some type of criminal act" before they were killed, the chief said.This was based on information from a witness who had been invited to join the men to "hit a lick big enough for all of them," Prentice said, quoting the witness."We do not know what they were planning or where they planned to do it," the chief added, noting that the term is commonly used for "engaging in some type of criminal behavior."On Friday, a passerby reported something suspicious in the water, leading authorities to find the human remains.