Police Activity on Mowry at Civic Center; Juvenile Bicyclists Cited

A motor officer requesting help at Mowry and Civic Center due to a large group of people throwing objects at the officers. Numerous officers responding code 3.  A minute later the crowd had dispersed.  Not sure if this began as a traffic stop or an accident investigation.  Now an officer on Stivers is out with a group of ten.
Update;  This is a group of bicyclists, some or all juvenile riders, that are the issue here.  This may be the same group that people have been calling about almost every weekend since last summer.  Sounds like at least a dozen of them and in the past they have been driving all over the hub and city streets causing near misses and hindering traffic.
Update:  A sergeant on scene advises that this is not the local group that had been causing problems, but a new crew from San Leandro-Hayward.  The Watch Commander does not want them getting any slack...doesn't want them to return to Fremont.  Officers will jack them up for no helmet and impeding traffic as they were riding in the two slow lanes of Mowry.  Also resisting arrest for those that fled when told to stop.  Some kids will be going to the station and their parents will be called, others will be issued a cite, depending on the severity of the crime.
More..numerous calls about these kids came in around 3:15 as they were on Mowry and Cherry, driving in the traffic lanes, doing wheelies, not letting cars pass, etc.  There were about 50 of them.  An officer said these were probably the same kids that were in Niles earlier.