Chief Constable Tim Forber said: “We are doing everything we can to support Rosie’s family, along with the family of a man who was also tragically killed in the incident.
“This is clearly a deeply traumatic and heartbreaking event for everyone involved and we ask that the two families are left alone to grieve in peace.
“Rosie’s response team colleagues in York, and from around the force, are being supported at this extremely difficult time.”
Her family have described PC Prior as “a loving mum, wife, daughter, sister, aunty and will be deeply missed”.
Mr Welford’s family said in a statement: “Ryan was a hardworking and loving father, husband, son and brother.
“He will be greatly missed by his family and friends.”
Anyone with any information on the incident should email mcit@northyorkshire.police.uk quoting reference number 12250006038.