The Railroad Serial Killer was an illegal from Mexico who probably killed on both sides of the border. It's not so much that someone is an illegal because most illegals are perfectly harmless people ----but there are some people who use the open border to commit horrible crimes. It's quite easy to murder on one side and then get to the other side to make it impossible for the police to catch up with you, there is a reason that so many pedophiles are living on the border on the US side.
I wonder how many children are missing on the Mexican side and if this killer decided not to go over to Mexico because of increased checks recently on the bridges.
The Juarez, Mexico murders alone are in the hundreds when it comes to murdered & missing children. Adults getting killed too. That's just one city on the Texas border.
Mrs K