DALLAS (CBSDFW.COM) – Two pedestrians and a motorcyclist were killed in three separate crashes in Dallas Thursday, authorities say.

The Dallas County Sheriff’s Department said the first incident happened in the afternoon after a pickup truck had stopped in the left lane of eastbound I-30 near Loop 12 after a ladder fell off of it. The driver got out to remove the ladder from the roadway.

The pickup truck was about to leave when a motorcycle slammed into it from behind, throwing the motorcyclist onto the left center lane of the highway.

Authorities said the motorcyclist, later identified as 41-year-old Gregory Suess, was transported to the hospital where he was pronounced dead at around 1:20 p.m.

Witnesses told authorities that the motorcycle was speeding through the highway and making multiple lane changes.

The second incident happened on northbound I-35E near Continental Avenue when a car struck a female pedestrian at around 9:45 p.m.

The driver told the sheriff’s department that he had hit something on the highway but didn’t know it was a person until after he stopped. Authorities said the body was thrown onto the left center lane and was hit again by an unknown vehicle.

The second driver who hit the woman did not stop.

The victim has not yet been identified but authorities believe she was 52 years old.

In a third incident, a pedestrian was hit and killed on southbound I-35E near Riverfront Boulevard at around 11:40 p.m. The victim hasn’t been identified but is said to be a 52-year-old man.

The driver who hit the man told detectives that he couldn’t swerve away in time when the victim was on the roadway

No arrests were made in either of the three deadly incidents from Thursday.