The bus was traveling southbound on I-94 in Milwaukee just before 10 p.m. Central time Friday, when authorities received at least two 911 calls from passengers. Schmaling said Vargas-Rosas had gotten into an argument with two other passengers and later, for reasons still unclear, threatened to shoot everyone on board as he dug into his waistband. He also was acting suspiciously, pacing back and forth and going in and out of the washroom, Schmaling told reporters.
Officers tried to stop the bus, but it kept traveling nearly 20 more miles south toward Illinois, passing Racine and Kenosha counties in Wisconsin. Schmaling said the bus driver was oblivious to what had been happening on the bus and did not realize that officers were trying to pull him over.
The bus finally stopped in Wadsworth, Ill., just south of the border, after officers spiked the tires. Vargas-Rosas surrendered, but later threatened investigators as he was being interviewed, Schmaling said.
No one was injured.
A Greyhound spokeswoman initially said that 50 passengers were on the bus, but Schmaling told reporters Saturday that the vehicle was carrying 37 people, including the driver and the suspect.
A second bus transported the passengers to their destinations, according to Greyhound.
Police shut down I-94 near the Wisconsin-Illinois state line until the suspect was arrested, according to media reports.
Alisa Tang contributed to this article.