I always thought riptides were associated with conflicting onshore tides competing against outward flows from major rivers.
first, he appears to have drowned from a rip current, and not a rip tide. The two are not the same thing, though it's not uncommon for people to call rip currents rip tides.
From NOAA: "Rip currents are not rip tides. A specific type of current associated with tides may include both the ebb and flood tidal currents that are caused by egress and ingress of the tide through inlets and the mouths estuaries, embayments, and harbors. These currents may cause drowning deaths, but these tidal currents or tidal jets are separate and distinct phenomena from rip currents. Recommended terms for these phenomena include ebb jet, flood jet, or tidal jet."
Rip currents are in no way associated with the flows from major rivers. Along the Jersey shore, I've seen rip currents scores of times, and been caught in rip currents a few times, and none of these situations were anywhere near a river, or even an outlet from a bay or inlet. From the NWS: "Rip currents form when waves break near the shoreline, piling up water between the breaking waves and the beach. One of the ways this water returns to sea is to form a rip current, a narrow stream of water moving swiftly away from shore, often perpendicular to the shoreline."