Over the weekend, two pedestrians were struck by drivers who didn't immediately stop following the collisions. In both cases, the victims were seriously injured.

At 10:10 p.m. on Friday, San Francisco Police Department spokesperson Officer Gordon Shyy says that a taxi struck a pedestrian who was in the crosswalk at Bay Street and Buchanan Streets in the Marina District.

According to Shyy, the cab driver initially fled the scene, then returned a short time later. The Chron reports that the cab driver, 62-year-old Vallejo man Raymond Rodriguez, was cited for speeding, but Shyy hastens to add that the incident remains under investigation.

Based on a photo on CBS5's website, Rodriguez appeared to be driving for Arrow Checker Cab.

According to Shyy, the man Rodriguez allegedly struck, identified only as a man in his 20s, was transported to the hospital with a broken leg and contusions to the upper body. His condition was unknown at publication time.

In a second collision, on Sunday night at around 7:30 p.m., Shyy says that a driver struck a pedestrian at Duboce Avenue and Valencia Street in the Mission District.

The Chron reports that witnesses say the pedestrian “ignored the light," and possibly entered the intersection against the signal.

After leaving the victim with life-threatening injuries, the driver stopped two blocks away, on Market Street, Shyy said. It's unclear why they kept driving following the collision, which had been severe enough to send the victim over the car's hood and couldn't have gone unnoticed.

According to the Chron, both the driver and a passenger "were detained pending an ongoing investigation into the circumstances leading up to the collision." The pedestrian was transported to San Francisco General Hospital, and an update on their condition wasn't available at publication time.