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Authorities this week are examining weapons seized from the home of a teenager they say opened fire at Saugus High School and are scrubbing social media accounts, trying to learn more about what spurred the violence that left two students dead and three wounded in Santa Clarita.

Los Angeles County Sheriff’s Department homicide Capt. Kent Wegener said the federal Bureau of Alcohol, Tobacco, Firearms and Explosives was examining a cache of unregistered weapons seized from the home of Nathaniel Berhow. In addition, homicide detectives are working with the U.S. Secret Service to examine the teen’s electronics and social media accounts. An Instagram account initially thought to belong to Berhow was a hoax created by someone in the aftermath of the shooting, Wegener said.

Results of both the weapons and electronics investigations are expected by the end of the week, authorities said.

Officials remain unsure about where the .45-caliber handgun used to carry out the attack Thursday morning was acquired. They are trying to determine whether the gun was made from parts purchased separately and then assembled, law enforcement sources told The Times. Such weapons, known as “ghost guns,” do not have serial numbers and can be manufactured from parts ordered through the mail or acquired from underground makers.

Read the full story on LATimes.com.