One cyclist is dead and another injured after two separate vehicle collisions Sunday. In one, a bike rider was killed beneath the tires of a Muni bus; and in the other a cyclist and horse trailer collided, leaving her injured.

According to San Francisco Police Department spokesperson Officer Grace Gatpandan, it was 3:22 on Sunday afternoon when police were called to the 500 block of Market Street (which is between Sutter and First Streets), on reports of a collision between a Muni bus and a cyclist.

"At this time," Gatpandan says, "it appears the both the bicyclist and bus were were traveling westbound on Market Street when the bicyclist lost control and collided with the bus."

Hoodline reports that the bike rider "maneuvered out of the sharrow lane to ride between two buses," and quotes SFMTA spokesperson Paul Rose as saying that "It does not appear the bicyclist was traveling in a bike lane." Which is an odd thing to say since, as Hoodline notes, "there is not a bike lane on that section of Market Street. Instead, one lane is designated to be shared by cars, Muni buses and cyclists."

After the collision, the rider, who Gatpandan describes as "a white male, 48 years old, and he was wearing his helmet," was wedged beneath the tires of the bus with which he had collided. He died at the scene. KQED has since identified him as Mark Heryer, a 48-year-old Berkeley resident.

"The cause of the collision is under investigation and no determination of fault has been made," Gatpandan says. "Investigators will take into account the time of day, road conditions, traffic conditions, as well as any video surveillance which may have captured the incident."

ABC7 reports that as part of the investigation, "people aboard busses were offloaded and questioned to see if they saw anything."

"We're pulling that vehicle as well to look at that video, but this is the coach where contact was made and we're working with the police department to do everything we can to find out what happened to deal with this the best way we can," Rose told ABC7.

The driver will also undergo drug and alcohol testing, as is protocol in all Muni collisions.

Gatpandan emphasized to CBS5 that "officers will conduct a thorough investigation because 'the victim can’t speak for himself.'"

"Don't try to pass a bus," Gatpandan also said to Hoodline, "especially in the streetcar lane. Stay to the right."

Sunday afternoon, the SFMTA released a "Statement of Condolences from SFMTA Director of Transportation, Edward D. Reiskin," which read in part that the transit agency "wish[es] to express our deepest sympathies and condolences to the family and friends of the cyclist who lost his life in a bus collision along Market Street late this afternoon."

"Our agency will work closely with SFPD to ascertain all facts of this truly unfortunate event," the statement read, noting that "The SFMTA adopted a Vision Zero Policy in 2014, with the goal of eliminating all traffic deaths in San Francisco by 2024. We are committed to working with our partners to make San Francisco streets safer, while educating the public on traffic safety, enforcement of traffic laws and prioritizing the necessary resources that implement life-saving initiatives."

The San Francisco Bicycle Coalition also released a statement on the fatality, saying that "We cannot achieve Vision Zero -- our City's goal to eliminate traffic deaths and severe injuries by 2024 -- without the three E's: engineering, education and smart enforcement."

"Today's tragedies demonstrate yet again that our City's elected leaders and agencies owe it to the growing number of people here who bike, and to the families of those who can no longer join them, to redouble their efforts and investments to deliver engineering solutions without delay, expand safety education, and ensure that the SFPD's priorities honor yesterday's tragedies and data through smart enforcement tomorrow," the SFBC wrote.

The SFBC uses the plural because less than 30 minutes later, there was a second collision between a cyclist and a vehicle. At 4:01 p.m., Gatpandan says, police were called to Chestnut Street and The Embarcadero.

When officers arrived, they discovered that a 46-year-old female cyclist "had collided with a horse trailer, suffering wounds to the head."

The cyclist was transported to San Francisco General Hospital with injuries that are not considered life-threatening, Gatpandan says. Hoodline reports that Gatpandan says she had been wearing a helmet, which "was a 'huge factor' in the woman's injuries not being life threatening."

"The driver of the truck remained on scene and is cooperating with police. At this time, investigators have determined drugs and alcohol are not a factor," Gatpandan says, but did not have additional details of that collision as of publication time.

Gatpandan says that both of these collision cases are "open and active," so anyone with information on either is encouraged to contact SFPD's Anonymous Tip Line at 415-575-4444 or to text a tip to TIP411 with SFPD at the beginning of the message.