How to escape Cerberus: without dying twice

Two Heads

RD's eardrums ached even more with each vociferous stomp sounding behind him as he frantically ran. Pumping adrenaline surged through him as he stumbled on, looking to escape the grasp of the ravenous three-headed hellhound, Cerberus. He didn't dare look back for whatever life he still had because he knew what sight would await him, and he was not ready to face that.
          The longer RD ran, the clearer his revelation came that maybe this was a bad idea. His group of about twenty or so was diminished to a mere five souls: Nathaniel Prota, Zoe Defter, Avia Thana, Synthia Tetra (and himself). They scattered across the rocky terrain of which belonged to the River Styx, desperately hoping to confuse the Underworld's spawn that continued to chase relentlessly after them. Its three heads swiveled in every which way, forcefully bumping into each others' and causing awfully high-pitched, ear-bleeding whines to erupt. That was a short-lived victory, RD realized, as Cerberus regained its composure and fortunately stumbled towards the not-so-fortunate Prota and Defter out in the open. The last thing he saw before running away was the harmonious screeching of the two psyches, reigniting the will within him to escape the gluttonous beast.
           As the trio of survivors, if they could be called that, continued running - they found themselves on a mountainside, narrowly missing a second death. RD rounded a boulder before skidding to a stop. He peered over his shoulder and saw Avia Thana throwing herself overboard, as if clouded by a sudden delusional state. She laughed mindlessly, flapping her arms as she fell to her death. Synthia Tetra, a step behind Thana, stopped right before she plummeted off the cliff. She quickly turned around and screamed in terror as the multi-headed hound opened its mouth to consume her. However, before either of them could react, RD somehow managed to launch the boulder right onto Cerberus' middle head. Unfortunately, within a fortunate deed, Synthia Tetra was also crushed.
         The sound of agony was definitely heard up to Hades' palace. The hellhound roared, making sure its threat was made clear. Where its middle head used to stand was now nothing more than a bloody log, the other two heads furiously spazzing out in pain. RD stood frozen in shock from his poor judgement of coordination, his plan of slowing down the hellspawn costing Tetra her life. It wasn't until a snarl brought him back to reality, forcing him to move his already sore legs closer to the river.
         Cerberus mercilessly pursued RD. He nearly tripped several times, and there came a point where he did stumble and fall backwards before springing right back on his feet. The dog was only a couple of feet away. It now approached cautiously as it got closer to the abyss of distressed souls. RD looked between the Styx and Cerberus. Without another thought, he dove.