Bruce Miller, a former fullback for the 49ers, allegedly used social media to threaten Democratic congressman Eric Swalwell.

Swalwell posted a screenshot of a private message from Miller, which read, “Would you rather Guantanamo or just execution.”

According to NBC, Swalwell notified U.S. Capital Police of the message.

“My family and staff are deeply disturbed by the threat of execution…apparently by former 49er Bruce Miller,” Swalwell told NBC’s Raj Mathai. “Threats of political violence are unacceptable.”

Swalwell did not know who Miller was, wondering with his initial post why the account had nearly 55,000 followers.

“Who is this guy threatening to execute me? And how does he have so many followers?” Swalwell posted with the initial screenshot.

Swalwell, who represents California’s 14th district, unsuccessfully ran for president in the 2020 Democratic primary.

Miller did not respond to a direct message from The Post in time for publication.

Miller, who played for the 49ers from 2011-15 before making a brief return in 2020 with the Jaguars, has been arrested twice in the past.

In 2015, he pleaded no contest to a disturbing the peace misdemeanor after destroying a woman’s cell phone.

The next year, he was arrested for assault and elder abuse, with police alleging that he attacked a 70-year-old man and his 29-year-old son.

The 49ers released Miller following the second incident.

He finished his career with 736 receiving yards and three touchdowns, with his comeback attempt in 2020 being marred by a six-game PED suspension, as he played just eight games for the Jaguars before getting released in late October.