Waiting by the tracks were Jim, Thornton and a new recruit named Harrison Askew. As the train rolled to a stop, Askew lost his nerve and fled the scene.

Once the train had stopped, Rube and Bromley ordered the engineer and fireman to the express car while Jim and Thornton held the other railroad workers at gunpoint.

As Rube sought entry to the express car, the messenger of the Pacific Express Company refused to open the door. The robbers responded with a barrage of gunfire, about fifty or sixty rounds were fired. The outgunned messenger opened the express car, surrendering an estimated 2,275 dollars and the US Mail bags, which contained another 2,000 dollars.

As the brothers became aware of more trains carrying money, they planned more robberies. They were making far more money robbing trains than they could ever hope to earn farming or ranching. In time, following a string of robberies, the Pinkerton Agency was hired to track them down.

In June of 1887 the gang boarded the Texas & Pacific Express in Ben Brooks, Texas and ordered the engineer to stop the train on a trestle outside of the town. The amount of money taken in that robbery is unknown, but on September 20, 1887, the gang robbed the train again, this time taking between 12,000 and 30,000 dollars, according to newspaper reports.

As the pressure from lawmen mounted, Rube decided to darken his hair to help disguise himself and return to Alabama, where he could hide out in relative safety. He was not yet aware that his name was unknown to those in law enforcement.

While in Alabama, he organized another gang and Rube was back in the business of robbing trains. During this time, Rube shot and killed one passenger and a postmaster, who had refused to surrender a cashbox.

On December 9, 1887, at Genoa, Arkansas, Rube, Jim and Jim Brock robbed the St. Louis, Arkansas & Texas Railroad express train of a large amount of money, in spite of the fact that the Southern Express Company had guards posted aboard the train. The Southern Express Company was closely associated with the Pinkerton Detective Agency and it was this robbery that brought Rube Burrow to the attention of the Pinkertons.

A local deputy sheriff told the Pinkertons that he had seen three suspicious men in the area on the day of the robbery, one of them had dropped a raincoat. The label in the raincoat showed it to have been from a store in Dublin, Texas. The Pinkertons contacted the store and a store clerk identified the purchaser as Jim Brock. Jim Brock was located and placed in custody. He confessed to having been a part of the robbery and identified the leader of the gang as Rube Burrow. Prior to this, Rube's name was not known to authorities.

Rube was not yet aware of Brock's arrest as the Pinkertons tracked him. They managed to get a letter that Rube had written that had a return address in Lamar County, Alabama. On January 8, 1888, the Pinkertons surrounded the Burrow homestead, but Rube had been warned of their intentions by his brother, Jim, and he fled.