BROWNSVILLE, Texas (WJW) – The FBI has asked for the public’s help in finding four U.S. citizens who were assaulted and kidnapped in Mexico.

Four Americans inside a white minivan with North Carolina license plates crossed into Matamoros, Tamaulipas, Mexico on Friday. Shortly after crossing into Mexico, gunmen fired toward the passengers in the vehicle, according to Oliver Rich, special agent in charge of the San Antonio Division of the Federal Bureau of Investigation.

All four U.S. citizens were then put into a vehicle and taken from the scene by men with guns, according to the FBI.

The FBI, federal partners and Mexican law enforcement agencies are investigating.

The FBI announced a reward of $50,000 for the return of the victims and the arrest of those involved.

Mexican President Andrés Manuel López Obrador said Monday the four were going to buy medicine, “there was a confrontation between groups, and they were detained,” without offering details.

A woman driving in Matamoros saw what appeared to be the shooting and abduction. She asked not to be identified for fear of reprisal.

“All of a sudden they (the gunmen) were in front of us,” she said. “I entered a state of shock, nobody honked their horn, nobody moved. Everybody must have been thinking the same thing, ‘if we move they will see us, or they might shoot us.’”

She said the gunmen forced a woman, who was able to walk, into the back of a pickup truck. Another person was carried to the truck by the gunmen but could still move his head.

“The other two they dragged across the pavement, we don’t know if they were alive or dead,” she said.