Mysterious explosion kills a Palestinian and a two-years-old child in Khan Younis

An explosion occured on June 28th at approximately 3.
15pm,in a house owned by Mohammad Masoud located in Al Aqqad area in Khan Younis downtown, killing Qassem Masoud, 26 and his two-years-old niece Maisam Masoud, injuring 4 others and damaging the house.
No further information on the incident nor whether the explosion was due to Israeli shelling.