Three foxes were shot in "absolutely shocking" and "disturbing" attacks last week, London's Metropolitan Police said.
Anyone in the UK with a credit card and an internet connection can buy one in minutes.
Ramanodge Unmathallegadoo is accused of murdering Devi Unmathallegadoo after she left him for another man.
Lee Atkins was shot by David Ball with the weapon in Bootle, Merseyside.
Medics were unable to save Devi Unmathallegadoo, but her baby was delivered by emergency Caesarean and survived.
Mystery surrounds deaths of 53-year-old man and two women aged 33 and 30.
Gerald Corrigan, 74, was shot on April 19, with the bolt narrowly missing his heart.
The 74-year-old suffered "horrendous, life-changing injuries".
Devi Unmathallegadoo was shot the abdomen as she attempted to flee. Her unborn baby survived the attack.
“He did not waste a second. He seemed like he had training.”