This is a standard practice for them. They shell a place and wait until the emergence services arrive. As they use drones for the attack and clearly see who they shell, there is no question that this is a deliberate practice. I've posted about some of the attacks:

Ukraine shelled a shopping center in Donetsk. When the rescuers arrived, the site was shelled again

Ukrainian drones hits Donetsk car repair service three times, injuring medics who arrived to help after the first attack

Ukrainian army posted a video where they shell an ambulance and emergency services, basically admitting and bragging about their war crime

In the DPR, four firefighters were injured by Ukrainian kamikaze drone

Ukraine repeatedly shelled Donetsk's center, killing civilians and emergency services workers.

Ukrainian drone hit an ambulance with evacuated from another shelling, killing one paramedic and wounding more