ANCHORAGE, Alaska (AP) — Police in Alaska charged four people with the killing of a 21-year-old man and arrested a fifth person with witness tampering.

The arrests were the result of an investigation into the death of Preston Atwood, whose body was found Aug. 30, the Seward Police Department announced Wednesday.

Atwood went missing from Fourth of July Beach in Seward on the Kenai Peninsula. He was last seen Aug. 25 around 6 p.m., authorities said.

Police charged two men and two women with murder, manslaughter, assault, conspiracy to commit murder, conspiracy to commit assault, and tampering with physical evidence.

Two people, including one of the suspects charged with murder, also face witness tampering charges.

“We would like to extend our deepest appreciation and thanks to Preston Atwood’s family and friends, and the Seward community for their assistance, support and patience as we conducted our investigation,” the Seward police said in a statement.

Police did not immediately respond to requests for additional information.