Man pleads not guilty to allegations of threatening a mass shooting at UC Irvine

A transient convicted of felony gun and ammunition charges pleaded not guilty Monday to threatening a mass shooting at UC Irvine and multiple weapons violations.

Sebastian Bogdan Dumbrava, 30, was charged with one count of delivery of a threatening letter with the intent to extort, one count of attempting to extort property or other consideration by means of a threat and five counts of the manufacture, sale or receipt of large-capacity a magazine that is prohibited, all felonies.

Dumbrava entered his plea in the jail courtroom in Santa Ana and was ordered to return to court April 27 for a pre-trial hearing in the Harbor Justice Center in Newport Beach.

Dumbrava made threats on Twitter and sent emails to UCI officials throughout 2019 and the beginning of 2020, according to an affidavit from UC Irvine police detective Samuel Soon.

The threats “referenced firearms, the Virginia Tech school shooting, the Virginia Tech active shooter and his self-identified six stressors that are common in active shooters,’’ Soon said.

Dumbrava also “made a comment about the possibility to acquire a firearm that can be used to indiscriminately massacre students,” Soon said.

Dumbrava was arrested Jan. 10, 2020, and convicted March 16, 2021, of unlawful possession of a firearm and a prohibited person owning ammunition, both felonies.

He was sentenced March 24, 2021, to three years and eight months in state prison, according to court records.

After he got out of custody, from October through December 2021, Dumbrava allegedly tweeted “Judge [Scott] Steiner stated that he believes I will commit a mass shooting at UC Irvine sometime next year, in 2022. He also apologized to the UC Irvine students that he believes I will massacre, stating that he is sorry that he cannot do more to prevent me from killing them.”

He allegedly later tweeted that he intended to commit a mass shooting in 2020 with the intention of causing financial injury to the university and “was close to killing a very large amount UC Irvine students in a very short amount of time,” blaming the regents of the university system for his actions by failing to provide restitution to him for perceived injuries.

Dumbrava was arrested Jan. 11, 2022, for violating terms of his probation, and investigators found receipts from gun stores in Arizona that were stored in his mother’s storage locker in Anaheim, Soon said.

After a flash incarceration, Dumbrava was released Feb. 23 and ordered to report to his probation officer but failed to do so, Soon said. That prompted an arrest warrant for Dumbrava, who had been living out of his mother’s car, the police detective added.

Dumbrava called his mother on Feb. 28 from a phone that blocked caller ID who “begged” him to turn himself in to authorities, Soon said.

Dumbrava was arrested by Garden Grove police on March 5 and sentenced to 90 days in jail for the probation violation, Soon said.

“He is a highly educated individual with an advanced comprehension of technology,” Soon said.

Dumbrava was placed on a mental health hold, and a search warrant was executed at his residence on Jan. 10, 2020, where investigators found 1,199 rounds of ammunition, 22 large-capacity magazines and various other loaded and unloaded weapons and parts required to make AR-15-style assault rifles, Soon said.

Staff writer Lilly Nguyen contributed to this report.

Support our coverage by becoming a digital subscriber.