You can avoid specifying agency in the active with some sort of placeholder. Hopefully, maybe, that placeholder is going to be more noticable than the omission of agency in the passive... but it seems more useful to simply ask directly whether agency is clear.
"Missiles were shot at Gaza" is passive and avoids specifying agency. "Someone shot missiles at Gaza" is active and avoids specifying agency. "Missiles were fired at Gaza by Israel" is passive and specifies agency. Sometimes you don't even need a placeholder: "Missiles hit Gaza" is active and avoids agency.
"Missiles were shot at Gaza" is passive and avoids specifying agency. "Someone shot missiles at Gaza" is active and avoids specifying agency. "Missiles were fired at Gaza by Israel" is passive and specifies agency. Sometimes you don't even need a placeholder: "Missiles hit Gaza" is active and avoids agency.