A teenager who opened fire with a 9 mm pistol in his Nashville high school cafeteria fired a total of 10 shots within 17 seconds of entering the room, according to police.

Solomon Henderson, 17, had gone into a bathroom and posted photos to social media just before he went to the cafeteria and opened fire, police said.

Henderson shot and killed 16-year-old Josselin Corea Escalante and shot and wounded a 17-year-old boy at Antioch High School around 11 a.m. Wednesday, according to police.

Henderson died in the cafeteria from a self-inflicted gunshot wound to the head, police said.

The injured boy suffered a graze wound and was treated and released, police said.

Authorities are still investigating how Henderson obtained the pistol, Nashville police said Thursday.

The gun was purchased in Arizona in 2022 and was not reported stolen, police said.

No firearms or firearm parts were found during Wednesday’s search of Henderson’s home, according to authorities.

Authorities are now scouring Henderson’s writings and social media presence as they investigate his ideological influences.

A Pinterest account linked to Henderson features photos of past school shooters, including the shooters from Parkland, Florida, and Uvalde, Texas, a source told ABC News.

Henderson’s social media presence also shows he may have been in contact with 15-year-old Natalie Rupnow, who carried out a shooting at the Abundant Life Christian School in Madison, Wisconsin, last month, according to law enforcement sources.

Rupnow, who went by Samantha, also died after the shooting, in which two were killed and several wounded. Rupnow’s account may have been following Henderson’s account at the time of the Wisconsin shooting in December, according to law enforcement sources.

It appears Henderson had two documents on “non-traditional websites, one 51 pages in length, the other 288 pages,” police said.

The 51-page document expressed violent white supremacist beliefs, sources told ABC News. He expressed self-hatred as a Black person, and he wrote of wishing violence on other Black people.

He also expressed violent hatred toward Jews and used antisemitic tropes and conspiracy theories to express his views, according to the sources. Henderson appeared to support neo-Nazi accelerationist and violent incel beliefs and expressed a desire to see genocide committed against racial and religious minorities, according to sources.

He belonged to online communities that promote violence and extremism, sources said, and some people in those groups publicly identified Henderson as the school shooter long before his identity was confirmed by authorities.

ABC News’ Victoria Arancio contributed to this report.